As a shock absorbing structure that is provided in a front portion of a vehicle so as to absorb an impact from ahead, there is a shock absorbing structure in which a shock absorbing member is disposed on a front surface of a rigid bumper reinforcement member so as to extend in a vehicle widthwise direction. The shock absorbing member may have various shapes. For example, Japanese Laid-Open Patent Publication No. 2004-224106 discloses a shock absorbing member (a bumper absorber) having a substantially lain U-shape in cross section. The shock absorbing member collapses when an impact is applied thereto, thereby absorbing the impact. Such a hollow shock absorbing member can absorb the impact more efficiently in comparison with a solid shock absorbing member that is capable of absorbing the impact while it is subjected to compressive deformation. This is because the hollow shock absorbing member may have a smaller amount of uncollapsed portion when the impact is applied thereto.
As another shock absorbing structure having the hollow shock absorbing member, as shown in FIG. 5, there is a shock absorbing structure 80 that has a shock absorbing member 70 having a bent shape in cross section. The shock absorbing member 70 is elongated in a vehicle widthwise direction and has a space 74 that is spread toward a vehicle rearward direction. The shock absorbing member 70 is disposed in a bumper cover 76 so as to be positioned on a front surface of a bumper reinforcement member 72, thereby forming the shock absorbing structure 80. In the shock absorbing structure 80, when an impact P from ahead is applied thereto by an impactor such as a pedestrian, first, as shown in FIG. 6(a), the impact P is received by a bent portion 71 positioned at a front end of the shock absorbing member 70. Next, as shown in FIG. 6(b), the shock absorbing member 70, when applied with the impact P, is moved rearwardly around the bumper reinforcement member 72, so as to be vertically opened thereby. As a result, the bent portion 71 can be broken. Further, as shown in FIG. 6(c), the shock absorbing member 70 can then be collapsed, so that bent portions 71a and 71b applied with the impact P can be relatively displaced rearwardly. Thus, the impact P can be absorbed. Further, as shown in FIG. 7, a load applied to the impactor at the moment, i.e., a value obtained by multiplying (decelerating) acceleration applied to the impactor by mass of the impactor, is relatively increased when the shock absorbing member 70 is broken (FIG. 6(b)), thereby generating a first load peak which is indicated by a reference symbol b in FIG. 7. Further, when the shock absorbing member 70 is completely collapsed and the bent portions 71a and 71b applied with the impact contacts the bumper reinforcement member 72 (FIG. 6(c)), the load becomes relatively further increased, thereby generating a second load peak which is indicated by a reference symbol c in FIG. 7. The shock absorbing member 70 thus constructed may have no uncollapsed portion because it is broken and collapsed. Therefore, the shock absorbing member 70 can be reliably displaced rearwardly, so that the impact can be absorbed.
Generally speaking, in a shock absorbing structure, there is a need to reliably absorb an impact when a vehicle collision happens. In addition, from a viewpoint of protecting an impactor, there is a need to reduce a maximum load applied to the impactor.